1. Field of the Invention
The present invention relates to a purge gas unit and a purge gas supply integrated unit, which are arranged to measure a flow rate of purge gas to be supplied to a process gas unit by use of a flow sensor and make feedback control on an open/close control valve based on a measurement result.
2. Description of Related Art
For instance, some semiconductor manufacturing processes include continuous processes in a chamber, e.g., a continuous deposition process on substrates and a cleaning process in the chamber, which are executed by selectively allowing a plurality of process gas units connected to the chamber to communicate with it. This technique is disclosed for example in WO 02/93053.
In this case, if process gas remains in the process gas unit, compositions of the process gas are liable to degenerate before being supplied to the chamber, resulting in a poor yielding percentage. To avoid such disadvantage, the process gas unit is connected to a purge gas line via a purge gas unit to dilute the process gas remaining in a flow passage with purge gas. To stabilize reactions in the chamber at that time, a total flow rate of purge gas needs to be continuously controlled to a fixed value to provide a stable dilution rate of the process gas. Conventional purge gas units are therefore arranged to measure a flow rate of purge gas to be supplied to the process gas unit by use of a flow sensor and make feedback control on an open/close control valve based on a measurement result thereof, thereby allowing purge gas to be supplied in fixed amounts to the process gas unit. This technique is disclosed for example in JP 11(1999)-294697A.
In the conventional purge gas unit, however, the purge gas line is connected to the open/close control valve through pipes. This configuration needs a large foot space (installation space).
Further, the conventional purge gas unit is arranged to receive purge gas through a purge gas common passage provided outside the unit. Thus, a pipe space is required for the purge gas common passage, resulting in a wider foot space. The number of purge gas units is increased in association with the installation of additional process gas units. As the number of arranged gas lines is increased, the foot space would be remarkably problematic. In addition, there is a recent demand for a semiconductor manufacturing system to reduce the apparatus size in order to shorten the gas line to enhance the accuracy of flow rate of process gas. Accordingly, downsizing of the purge gas unit has been requested.